Almost all AgX photographic materials normally contain spectrally sensitizing dyes (referred to hereinafter as sensitizing dyes) and antifoggants. The sensitizing dyes are used to extend the photosensitive wavelength region of the AgX from its intrinsic region to the long wavelength side (into the green, red, and infrared regions), and to increase photographic speed in the blue region. On the other hand, antifoggants are used to prevent the occurrence of fogging during the storage of the AgX photosensitive material (when they are known as emulsion stabilizers) and to prevent the occurrence of fogging during development (when they are known as development inhibitors). Both sensitizing dyes and antifoggants are therefore essential additives for AgX photographic emulsions. These additives are normally added using the following methods.
(i) Methods in which each additive is added individually. In some methods the total amount is added at one time, and in other methods the total amount is divided and added in several parts.
(ii) Methods in which the additives are mixed together prior to addition.
However, the following disadvantages arise when these additives are added using these conventional methods.
(1) Adsorption of the sensitizing dyes and antifoggants is competitive, and in some cases spectrally sensitizing dyes are desorbed and replaced by antifoggants while in other cases where the reverse is true. Accordingly, the most preferable spectrally sensitizing dyes and antifoggants for the photographic property can not be freely selected.
(2) In general, the adsorption of cyanine dyes on AgX is due principally to van der Waals forces and the strength of adsorption becomes weaker as the polarity of the substrate falls (in the order AgI.fwdarw.AgBr .fwdarw.AgCl). In the case of AgX emulsions which have a high chloride ion (Cl.sup.-) content in the grain surface, the strength of adsorption of sensitizing dyes is particularly weak and there is a problem in that it has not been possible to realize the preferred spectral sensitization.
(3) Antifoggants can generally be represented in the form (HL) of an acid, and the antifoggant becomes more strongly adsorbed as, on comparing the solubility product pKsp (AgL)=-log [Ag.sup.+ ] and the solubility product pKsp (AgX) for AgX, the difference [pKsp (AgL)-pKsp (AgX)] becomes greater. Accordingly, the strength of adsorption when using the same antifoggant will increase in the order AgI &lt;AgBr &lt;AgCl. This trend is the opposite of that observed in the case of the cyanine dyes and the undesirable reaction in which antifoggants desorb and replace cyanine dyes on AgX emulsions with a high Cl content referred to in (1) above is further advanced, and this is undesirable.
(4) In general, when cationic cyanine dyes are added to an AgX emulsion the state of adsorption changes from a state of single molecule type adsorption through a state in which aggregates of two or three molecules are adsorbed to a state in which larger aggregates are adsorbed as the adsorbed covering factor of the sensitizing dye increases, and there is an accompanying decrease in intrinsic speed and a reduction in color-sensitization efficiency. The following factors can be considered in connection with the decrease in speed.
a. A large local increase in the potential of the space charge layer occurs at the surface of an AgX grain in the locality of a cationic dye aggregate (since the cationic dye is adsorbed on the X.sup.- sites of the AgX crystal surface and the interstitial silver ion concentration is increased), and electron transfer from the sensitizing dye to the AgX layer is inhibited.
b. The interstitial silver ion concentration is increased in the vicinity of the said local surface, promoting latent image formation, and so the latent image is dispersed and the efficiency with which a developable latent image is formed is reduced.
c. Cationic dye aggregates on the AgX grain surface form a type of static potential with respect to the conductive electrons in the AgX grains and function as electron trap centers, reducing the latent image formation efficiency at the chemically sensitized nuclei.
d. Development inhibition is increased by the presence of large J-aggregates.
Control of the aggregate size is important since these undesirable effects normally become more pronounced as the said size increases. However, the sensitizing dye aggregate size increases in cases where sensitizing dyes and antifoggants have been added to an AgX emulsion and the most stable adsorption equilibrium has been established, and it is difficult to control the said size as desired. There are methods by which aggregate growth is stopped during growth, but this involves a metastable state and the stability is poor. Furthermore, there is no change in that the outcome is still uncertain. Hence there is a problem that it is not possible to adjust the sensitizing dyes to the most desirable state of adsorption from the photographic point of view.
(5) In cases where single molecules, aggregates of two or three molecules and aggregates of four or more molecules are all present in the state of adsorption of the dye as described in (4) above, the absorption spectral bands of these states will, in general, be different and so the overall spectral absorption band will be very wide. This is particularly undesirable in color photographic systems. This is because, in a color photographic system, the absorption spectra of each of the blue, green and red photosensitive layers should not extend to any great extent into the other color sensitive layer regions from the viewpoint of color reproduction. Hence a single adsorbed state and an absorption which has a narrow half value width is desirable, but at present it is not possible to achieve such control. There are many cases in which there are only J-aggregates and single molecules present, and in the region of saturated dye adsorption the dye will almost all be present as J-aggregates, but this region is often a region of reduced sensitivity and it cannot be used.
Hence, the discovery of AgX photographic materials in which at least one of the above mentioned problems (1) to (5) have been resolved is awaited.